Minimally invasive surgery improves survival after colorectal cancer resection

Abstract

The first randomized trial comparing laparoscopic and open colon cancer resection reported a survival benefit for laparoscopy in 2008 [1]. None of the subsequent trials could confirm this finding. Nevertheless, Fahim et al. conclude that laparoscopy might improve longterm outcomes based on a multivariable analysis of a retrospective threecentre cohort study including 4531 colorectal cancer patients treated between 2009 and 2018 [2]. Strictly following the levels of evidence, this paper does not overrule the absence of any survival impact of laparoscopy in metaanalysis of randomized trials, but it is still worthwhile to elaborate further on this topic. In their multivariable analysis, the lower Hazard Ratio of open surgery if compared to the univariable analysis (1.26 vs. 1.52) illustrates that there was still an impact of known confounding variables after applying the exclusion criteria of cT4/pT4 category, simultaneous metastasectomy and emergency surgery. But how much residual confounding might have been present? Previous abdominal surgery was equally distributed, but imbalances in type of previous surgery might have existed. For example, a huge incisional hernia or severe adhesions are likely overrepresented in the open group. Furthermore, multivisceral resections remained in the analysed cohort after excluding cT4/pT4 category, with a higher proportion in the open group. Although this variable was included in the multivariable model, residual confounding might originate from differences in the extent of multivisceral resection or type of affected organs (i.e. duodenum, pancreas). There should have been reasons for applying an open approach in the small minority of patients in most recent years (2016– 2018), and those reasons might have had a prognostic impact. During this period, minimally invasive surgery was fully implemented in the three Dutch high volume centres. Comparative cohort studies provide stronger evidence if institutions (almost) completely differ regarding the studied intervention, resulting in pseudorandomisation. The authors state in the discussion that they observed significant variation in surgical approach among the three centres, but the role of hospitaldriven allocation has likely been small. One of the most difficult confounding factors in comparisons of open and laparoscopic surgery, which is even not dealt with in existing randomized controlled trials, is related to the quality of surgery and/or surgeon. Better surgeons are likely to be overrepresented in minimally invasive surgery cohorts, because those surgeons might more frequently and more successfully apply difficult minimally invasive techniques. There are no existing methods to properly correct for this type of confounding, although quality assessment tools have been developed. The only way to eliminate this type of bias is to stratify for individual surgeon in randomized trials. Personally, I fully agree with the interpretation and conclusions of the authors. Their main explanations for worse longterm survival after open surgery are the incomplete recovery of health status and higher chance of surgery for incisional hernia and adhesion related small bowel obstruction. Furthermore, circumstantial evidence suggests better oncological control if reducing surgical trauma and preserving hostdefence against micrometastatic disease. Highest impact of laparoscopy is expected in patients that need extensive or highrisk surgery (e.g. T4, emergency resection), those who were excluded by Fahim et al. [3]. But there is no ultimate proof of a survival benefit of laparoscopic colorectal cancer surgery in the existing literature, inevitably resulting in nonbelievers and sceptics.